The present invention relates in general to printed circuit board arrangements and more particularly to an improved method and apparatus for automatically positioning and soldering highly miniaturized components on a printed circuit board wherein such components are optimally located.
Present day electronic circuitry is characterized more and more by its high density in an extremely compact, low volume packaging configuration. Efforts to continually increase the density and/or decrease the circuitry volume has resulted in smaller and smaller components to the point that some, such as resistors, capacitors and diodes and the like measure but a few millimeters in length and not much more than a millimeter in width. Handling these ultraminiaturized components is all but impossible by hand. Placement thereof on associated circuit boards is best effected by automatic placement machinery. Even here, however, the margin or error in positioning the same is extremely narrow because of the size of the components and problems in misplacement are common.
Some solutions for these misplaced microminiature components have been effected in prior arrangements. Notably, the most common approach has been a self correcting feature for these components during the soldering phase. That is, means are provided for shifting the component to its more optimum placement position during a softening or reflow of the pre-applied solder paste. However, this technique presupposes the microminiaturized components are positioned on top of the associated circuit board and are free to shift or move to a final position before the hardening of the reflow solder material Such techniques cannot provide satisfactory results for those miniature components positioned on the bottom surface of the circuit board during the final soldering step. If such components were free to move, they would simply fall off by reason of gravity or other forces at work.
There are, of course, circuit board assembly techniques that are known in the art which contemplate positioning and retention of components, microminiature or otherwise, on the bottom surface of the circuit board before final soldering. Reference is made to U.S. Pat. No. 4,139,881, issued February 1979. However, that patent is directed to a degaussing procedure for such components. It does not in any way address the problem of misplaced components which may cause short circuits or related failures.
Accordingly, what is needed is an arrangement which will permit the placement of components, microminiature or otherwise, on both sides of the printed circuit board, which will permit and accommodate a final soldering step, may it be reflow or waveline soldering or a combination of both, and wherein the position of such components will be at their optimized locations at least after final assembly has been effected.